Our overall goal is the construction of a detailed cytological map of the human genome in which gen loci and gene linkage groups are correlated with morphologically recognizable regions of chromosomes. These efforts will be extended to fine structure mapping in the mouse in order to elucidate evolutionary relationships. Conserved syntenic groups of genes will be identified and assigned to respective chromosome regions in both species. Approaches will include: a) expansion and refinement of our existing hybrid clone panel that contains defined human chromosome regions; b) the establishment of a murine clone panel for regional mapping; c) the use of cloned single copy mammalian DNA fragments and Southern blotting techniques to identify the location of homologous sequences within and between species, with emphasis on the mapping of the loci responsible for restriction fragment length polymorphisms (RFLP) and on mapping of members of multigene families and pseudogenes. We will extend gene mapping efforts to new classes of genetic markers, e.g. total cellular polypeptides identified by two-dimensional gel electrophoresis. Having determined that we can distinguish approximately 100 polypeptides of human origin in Chinese hamster x human somatic cell hybrids, we will correlate their expression with individual human chromosomes or chromosome regions. Genes for receptor molecules (the glucocorticoid receptor in mouse lymphocytes, and the receptors(s) for antigen plus H-2 products on mouse T cells) will be mapped using intraspecies somatic cell hybrids that are chromosomally stable. Segregant hybrid clones having lost the specific receptor(s) will be karotyped and the specific chromosome lost will be identified. It has become clear that the Y chromosome does not carry the structural gene for H-Y and that gene(s) on the X chromosome and/or on autosomes must play a role in H-Y antigen expression. We will utilize somatic cell hybrids derived from human males and rodent females to identify the human chromosomes involved in the expression of H-Y antigen. The chromosomal localizations of genes coding for and modulating the expression of liver-specific proteins will be established in rat hepatoma x human hybrids made with human skin fibroblasts, fetal liver fibroblasts or hepatocytes.